Microbial communities associated with filter materials in recirculating aquaculture systems of freshwater fish

The microbial communities associated with filter materials in closed recirculated systems of carp and goldfish were examined by the clone library method of 16S rRNA gene. The bacterial cells were efficiently recovered by the combination of six washing treatment and swabbing. The bacterial density on pebbles of well-conditioned recirculating water systems was 1.1×10⁷ cells g⁻¹ in the carp-rearing tank and 1.9×10⁸ cells g⁻¹ in the goldfish-rearing aquarium. The 91 cloned rDNA sequences were occupied by members within Alphaproteobacteria (52 clones belonging to 19 taxa), Betaproteobacteria (14 clones belonging to 8 taxa), Nitrospira (8 clones belonging to 1 taxon), Actinobacteria (6 clones belonging to 4 taxa), Bacilli (3 clones belonging to 3 taxa), Gammaproteobacteria (3 clones belonging to 3 taxa), Planctomycetacia (3 clones belonging to 3 taxa) and Sphingobacteria (2 clones belonging to 1 taxon). However, only three taxa, which are closely related to Hyphomicrobium denitrificans, Rhodovulum euryhalinum and Nitrospira moscoviensis, were commonly detected in both carp- and goldfish-rearing systems. These results reveal that there are great differences in both bacterial density and composition between the two different systems, and that the clone library constructed from carp-rearing tank is characterized by as many as 29 taxa of bacteria, and that those from goldfish-rearing aquarium is characterized by Hyphomicrobium facilis with occurrence of 42%. These results mean that at least 36% of total clones could utilize the inorganic nitrogen, NH₄⁺, NO₂⁻ or NO₃⁻, suggesting that they concern the dynamics of nitrogen in fish-rearing facilities equipped with the recirculating system.     

Design and performance of a recirculating aquaculture system for oyster larval culture

The major objective of this study was to introduce a newly designed recirculating aquaculture system (RAS) for oyster (Crassostrea angulata) larval culture. The system includes a culture tank, a suspended circular inlet‐pipe, an upwelling aeration pipe, combined “banjo” sieves and a bioreactor chamber containing microalgae life keeping installation. The system was designed to resolve three problems: (i) stranding of larvae caused by water level changes and aeration, (ii) physical clogging of the screens and also (iii) deterioration of diet microalgae. The culture tank, “banjo” sieve size, water flow rate and light intensity for maintaining microalgae activity were all designed according to the pattern of larval movement and feeding behaviour. Results of this study showed the best average SGR for larval length was 6.36%/d (9.5 μm/d) and survival rate was 80%, with initial rearing density of 50 larvae/ml, indicating the problems above were fully resolved. Consequently, the system is fit for larval culture in mass production of oysters.     

Implementation of an easily reconfigurable dynamic simulator for recirculating aquaculture systems

Methodology of Programmable Process Structures has been implemented and applied for the flexible automatic generation and simulation of Recirculating Aquaculture Systems. First, we implemented and validated the model for a pilot unit, based on short time experiments with Common carp (Cyprinus carpio), utilizing data and functionalities from the literature. Afterwards, starting from this model we generated a hypothetical single tank model of simulated increasing volume, to demonstrate how it supports the simplified, preliminary analysis, design and control of the possible multi-stage systems. We showed that the simulation of a single tank with an appropriately increasing volume makes possible to study the various control strategies, as well as to design the structure and the grading strategy of the multi-stage systems, without an increased combinatorial complexity. In the knowledge of the simulated increasing volume, we determined the volumes of subsequent stages by equidistant partitioning of the rearing time, algorithmically. Considering the available (or planned) tank volumes, this method makes possible to design a multi-stage system that approximately corresponds to the previously optimized single tank model. This conclusion was illustrated by the generation and simulation of the model for the respective multi-stage system.     

Hydrogen peroxide oxygenation and disinfection capacity in recirculating aquaculture systems

Hydrogen peroxide (H₂O₂) treatment is an alternative for disinfection in aquaculture, which may be advantageous as it dissociates and disinfects while increasing water oxygen concentration. Yet, accurate dosing remains undeveloped in Recirculating Aquaculture Systems (RAS). Dosage requirements can depend on organic burden, stocking density, feeding frequency, salinity, temperature and biofilter performance. The present case study investigated the dual effect of H₂O₂ application for oxygen enrichment and disinfection when continuously applied to a RAS rearing European seabass. H₂O₂ addition equivalent to 2.4 and 15.8 H₂O₂ mg L⁻¹ were applied for 4 h per day in three 5-days experiments. H₂O₂ was injected at the inlet of protein skimmer and/or the rearing tanks in or without combination with traditional disinfection methods. Water microbial load and oxygen saturation were determined, along with stress markers glucose and cortisol in blood plasma of fish. Doses of 15.8 mg L⁻¹ H₂O₂ steadily increased oxygen levels in holding tank water from ∼50 % to over 100 % saturation while reducing microbial load (from 604.4 CFU ml⁻¹ in the rearing tanks before dosing to 159.8 CFU ml⁻¹ after application), achieving suitable conditions for commercial fish densities in RAS. The doses used had negligible impact on biofilter performance and did not affect the fish in terms of stress. Overall results indicate H₂O₂ is effective for disinfection and oxygenation of RAS systems when applied at appropriate dosage and we recommend the protein skimmer as the safest position in order to protect the bacterial community of the biofilters and the reared fish.     

鲟鱼工厂化循环水养殖系统设计及运行效果

针对目前中国淡水工厂化循环水养殖系统建设和运行成本过高,推广应用受到一定程度制约的问题,在自主研发斜管重力滤沉淀装置、内循环流化床反应器、一体化臭氧接触反应器等水净化设备的基础上,通过应用物质平衡相关原理,精确设计、确立不同阶段系统关键运行参数,建立一种高效节能的鲟鱼工厂化循环水养殖系统。通过96 d养殖试验,结果显示,鲟鱼摄食和生长情况正常,养殖密度平均(41.2±2.3)kg/m~3,存活率95.8%,饲料系数1.17。日换水量在5%以下,水质情况良好,氨氮和亚硝酸盐氮后期稳定控制在(0.80±0.21)mg/L和(0.38±0.12)mg/L;系统平均日耗电量为33.3 kW·h,平均产出1kg鲟鱼耗电7.30 kW·h。系统运行具有低能耗、高效率的特点,可为鲟鱼循环水养殖提供技术支撑。     

Tilapia recirculating aquaculture systems as a source of plant growth promoting bacteria

A recirculating aquaculture system with farmed tilapia is the most popular combination in aquaponics, an integration of aquaculture and hydroponics. Despite nutrient‐rich fish‐rearing water being regarded as a valuable resource for aquaponics, the quality and value of inhabitant microorganisms are certainly understudied. Our present research illustrates the feasibility of the tilapia‐rearing water as a valuable source of beneficial microorganisms called plant growth promoting bacteria (PGPB). Microbial communities were examined with a combination of culture‐independent high‐throughput 16S rRNA gene sequencing and cultivation methods. Microbial communities determined using high‐throughput sequencing indicated the usefulness of Bacteroidetes and Alphaproteobacteria as beneficial microbial indicators to assess the health condition of recirculating aquaculture systems. Siderophore production, ammonia production and phosphate solubilization assays were used for screening and 41% of isolates were identified as plant growth promoting bacteria. These bacteria were classified as Actinobacteria (eight strains [32% in total], Dietzia, Gordonia, Microbacterium, Mycobacterium and Rhodococcus), Bacilli (six strains [24%], Bacillus and Paenibacillus), Flavobacteriia (one strain [4%], Myroides), Betaproteobacteria (two strains [8%], Acidovorax and Chromobacterium) and Gammaproteobacteria (eight strains [32%], Aeromonas, Plesiomonas and Pseudomonas). We found that the tilapia‐rearing water naturally contained various lineages of PGPB and could be esteemed as a worthy seed bank of PGPB. Because aquaponics is a difficult system to use pesticides and herbicides, the role of PGPB to prevent plant pathogens and maintain healthy root system may be more important than traditional agricultural settings.     

Design and performance of recirculating aquaculture system for marine finfish broodstock development

Tropical and subtropical climatic conditions in India present an ideal and unique opportunity for being the leader in tropical marine finfish aquaculture. However, the problem persist due to non-availability of marine finfish seed for the culture. In response to this problem, broodstock development of different tropical marine finfishes for seed production was started. The present study was undertaken to design a recirculating aquaculture system (RAS) and studying their performance in managing the various water quality required for the marine finfish broodstock development and breeding. The design of RAS, developed in the present study, included a broodstock tank, egg collection chamber, electrical pump, rapid sand filter, venturi type protein skimmer and biological filter. Two RAS were designed, one was stocked with a demersal fish species, orange spotted grouper (Epinephelus coioides) and the other was stocked with a pelagic fish species, Indian pompano (Trachinotus mookalee) at the rate 1 and 0.5 kg/m³ with a sex ratio of 1:1 and 1:2 (female: male) respectively. Various physio-chemical parameters, viz, total ammonia nitrogen (TAN), nitrite, nitrate, pH, alkalinity, temperature, free carbon dioxide (CO₂) and dissolved oxygen (DO) of both tank water were analyzed to assess the performance of recirculating aquaculture system in maintaining the water quality. Gonadal development of the fishes was assessed and the spawning performance was recorded and finally, economic performance of the system was also evaluated. During the entire experimental period, mean monthly total ammonia nitrogen was less than 0.07 and 0.06 mg L⁻¹ and mean monthly nitrite was less than 0.02 and 0.01 mg L⁻¹ in orange spotted grouper and Indian pompano RAS tanks respectively. The pH (7.8–8.2), DO (>4 mg/L) and alkalinity (100–120 mg/L) were found to be in optimum range in both recirculating aquaculture systems. Carbon dioxide was found to be nil during the entire experimental period in both the systems. In fact these levels were comparable or less than that is reported as the permissible limits for broodstock development. Indian pompano and Orange spotted grouper matured and spawning was obtained with production of fertilized eggs round the year. Economic evaluation showed the price of 10,000 fertilized eggs of orange spotted grouper to be US $ 1.33. The design of RAS devised in the present study is efficient in controlling and maintaining optimum water quality for broodstock development of both demersal and pelagic finfishes. The fishes stocked in RAS attained final maturation and round the year spawning was obtained.     

Peracetic acid degradation and effects on nitrification in recirculating aquaculture systems

Peracetic acid (PAA) is a powerful disinfectant with a wide spectrum of antimicrobial activity. PAA and hydrogen peroxide (HP) degrade easily to oxygen and water and have potential to replace formalin in aquaculture applications to control fish pathogens, for example the ectoparasite, Ichthyophthirius multifiliis.We studied water phase PAA and HP decay in three aquaculture situations, i) batch experiments with two types of system waters, ii) PAA decay at different fish densities, and iii) degradation of PAA in submerged biofilters of recirculating aquaculture systems (RAS). Furthermore, effect of PAA on the nitrification activity and the composition of the nitrifying population were investigated.PAA and HP decay showed first order kinetics. High dosage PAA/HP in water with low COD inhibited HP removal, which was not observed in water having a higher COD content. PAA decay was significantly related to fish stocking density, with half life constants for PAA of 4.6 and 1.7 h at 12 and 63 kg m^− 3, respectively.PAA application to RAS biofilter showed rapid exponentially decay with half life constants of less than 1 h, three to five times faster than the water phase decay rates.Biofilter surface specific PAA removal rates ranged from 4.6 to 13.9 mg PAA m^− 2 h^− 1 and was positively correlated to the nominal dosage. Low PAA additions (1.0 mg L^− 1) caused only minor impaired nitrification, in contrast to PAA application of 2.0 and 3.0 mg L^− 1, where nitrite levels were significantly increased over a prolonged period, albeit without fish mortality. The dominant ammonium oxidizer was Nitrosomonas oligotropha and the dominant nitrite oxidizer was Nitrospira. Based on the present findings and other recent results from field and in vitro studies, application perspectives of PAA are discussed.     

Nitrate removal effectiveness of fluidized sulfur-based autotrophic denitrification biofilters for recirculating aquaculture systems

There is a need to develop practical methods to reduce nitrate–nitrogen loads from recirculating aquaculture systems to facilitate increased food protein production simultaneously with attainment of water quality goals. The most common wastewater denitrification treatment systems utilize methanol-fueled heterotrophs, but sulfur-based autotrophic denitrification may allow a shift away from potentially expensive carbon sources. The objective of this work was to assess the nitrate-reduction potential of fluidized sulfur-based biofilters for treatment of aquaculture wastewater. Three fluidized biofilters (height 3.9 m, diameter 0.31 m; operational volume 0.206 m³) were filled with sulfur particles (0.30 mm effective particle size; static bed depth approximately 0.9 m) and operated in triplicate mode (Phase I: 37–39% expansion; 3.2–3.3 min hydraulic retention time; 860–888 L/(m² min) hydraulic loading rate) and independently to achieve a range of hydraulic retention times (Phase II: 42–13% expansion; 3.2–4.8 min hydraulic retention time). During Phase I, despite only removing 1.57 ± 0.15 and 1.82 ± 0.32 mg NO₃–N/L each pass through the biofilter, removal rates were the highest reported for sulfur-based denitrification systems (0.71 ± 0.07 and 0.80 ± 0.15 g N removed/(L bioreactor-d)). Lower than expected sulfate production and alkalinity consumption indicated some of the nitrate removal was due to heterotrophic denitrification, and thus denitrification was mixotrophic. Microbial analysis indicated the presence of Thiobacillus denitrificans, a widely known autotrophic denitrifier, in addition to several heterotrophic denitrifiers. Phase II showed that longer retention times tended to result in more nitrate removal and sulfate production, but increasing the retention time through flow rate manipulation may create fluidization challenges for these sulfur particles.     

A comparison of topologies in recirculating aquaculture systems using simulation and optimization

Recirculating aquaculture systems (RAS) are often designed using simplified steady-state mass balances, which fail to account for the complex dynamics that biological water treatment systems exhibit. Because of the very slow dynamics, experimental development is also difficult. We present a new, fast and robust Modelica implementation of a material balance-based dynamic simulator for fish growth, waste production and water treatment in recirculating aquaculture systems. This simulator is used together with an optimization routine based on a genetic algorithm to evaluate the performance of three different water treatment topologies, each for two fish species (Rainbow trout and Atlantic salmon) and each in both a semi-closed (no denitrification) and a fully recirculating version (with denitrification). Each case is furthermore evaluated at both saturated and supersaturated oxygen levels in the fish tank influent. The 24 cases are compared in terms of volume required to maintain an acceptable TAN concentration in the fish tank. The results indicate that the smallest volume is obtainable by introducing several bypass flows in the treatment system of a semi-closed RAS and that the gains can be significant. We also show that recycling already treated water back upstream in the treatment process degrades performance and that if one wishes to have a fully recirculating system with minimal water exchange, then the flows of oxygen, carbon and nitrogen must be carefully considered. For several of the cases, no optimum with denitrification could be found. We thus demonstrate that the best configuration and operation strategy for water treatment varies with the conditions imposed by the fish culture, illustrating the complexity of RAS plants and the importance of simulations, but also that computer-driven optimal design has the potential to increase the treatment efficiency of biofilters which could lead to cheaper plants with better water quality.     

多层水槽式工厂化循环水养殖系统智能投饲车设计

为解决多层水槽式工厂化循环水养殖模式中人工投料操作空间局促、劳动强度大、饲料利用率低等缺点,设计了一套基于K60单片机的小微型智能投饲车。该投饲车由循迹小车、投饲装置和控制系统等组成,在特定投饲跑道上行驶,根据红外对管采集的轨道信息和压力传感器采集的饲料信息判别是否投饲或补料,进而实现智能定点定量投饲。初步试验运行结果显示,该投饲车运行稳定可靠,运行速度0. 5～2. 2 m/s,投饲的定位精度误差在2 cm以内,投饲量误差在10 g以内,基本满足设计要求。     

小丑鱼室内循环水养殖设施与技术

为了实现规模化人工养殖小丑鱼(Amphiprioninae),研发了小丑鱼室内循环水养殖设施和技术。1组循环水养殖系统由10个玻璃钢养殖桶和1个水处理玻璃缸及管道系统组成,采用物理过滤、生化过滤、藻板过滤进行循环水处理。1组循环水养殖系统每3个月可养殖产出全长约3.5 cm的商品小丑鱼5 000尾,养殖存活率达80%以上。从2014年至2015年,利用该设施养殖生产出商品小丑鱼10余万尾。和常规的食用海水鱼循环水养殖设施相比,小丑鱼室内循环水养殖系统主要减少了蛋白分离器、气浮机、微滤机等设备,增加了藻板过滤设施。研究表明,小丑鱼室内循环水养殖系统建造成本低、运行能耗低、管理维护简单、水质稳定,可基本实现全封闭循环水养殖,适合进行小丑鱼等海水珊瑚礁观赏鱼类的规模化养殖生产。     

Design criteria for recirculating, marine ornamental production systems

While recirculating aquaculture systems for food animals are well defined in the literature, little information is available for the emerging production of high value marine ornamental species. These organisms typically require systems which operate within a narrow range of parameters compared to most food animals, and in addition to growth and survival issues, individual appearance of animals is critical to success. This paper is a general review of the primary design criteria parameters for the production of marine ornamental species in stable, oligotrophic, recirculating aquaculture systems.     

Membrane performance and fouling behavior of membrane bioreactors installed in marine recirculating aquaculture systems

Accumulation of fine suspended solids and colloids in a recirculating aquaculture system (RAS) can be avoided by integrating a membrane filtration unit into the system, where the inclusion of a membrane bioreactor (MBR) may be an alternative. The main purpose of the study was to identify how the feeding regime affected membrane performance and fouling phenomena caused by dissolved and submicron colloidal particles in the system, and how the membrane impacted general water quality and particle characterization. To be able to evaluate membrane performance and fouling behavior, transmembrane pressure (TMP) was monitored and assessed in relation to changes in rearing conditions and different water quality parameters observed. From this study the positive influence on the chosen water quality parameters was apparent, where an improved water quality was observed when including a membrane filtration in RAS. Selected water quality parameters and TMP changed during the experimental period in response to the feeding regime, where algae paste, decaying rotifers and dry feed seemed to contribute the most to membrane fouling. Analysis of the concentration of submicron particles and particle size distribution (PSD) (particles < 1 μm) showed both a higher concentration and a more spread distribution in the rotifer/algae paste and dry feed period compared to the Artemia period, which might explain the observed increase in fouling. This study also showed that adapted procedures for concentrate removal are important to prevent hydrolysis of retained particles in the concentrate and leakage of nutrients and organic matter back to the system.     

Design and operation of nitrifying trickling filters in recirculating aquaculture: A review

This review deals with the main mechanisms and parameters affecting design and performance of trickling filters in aquaculture. Relationships between nitrification rates and easily accessible process parameters, like bulk phase concentration of TAN, O₂, organic matter (COD), nitrite, temperature, HCO₃⁻, pH and the hydraulic loading of the trickling filter, are discussed in relation to the design and operation of such filters. Trickling filter design procedures are presented and one of them, a model describing the nitrification performance of trickling filters by plug-flow characteristics, is discussed in greater detail. Finally, practical aspects in relation to filter design and operation are presented.     

An evaluation of solid waste capture from recirculating aquaculture systems using a geotextile bag system with a flocculant-aid

Two separate geotextile bag systems were evaluated as a means for capturing and dewatering bio-solids in the effluent stream from recirculating aquaculture systems (RAS). Each geotextile bag system used a high molecular weight cationic polyacrylamide (PAM) polymer as a flocculant-aid. The two systems were operated under freshwater and brackish water conditions. A complete analysis including water quality and agronomic sludge analysis was conducted at the North Carolina State University Fish Barn – a large-scale, freshwater RAS demonstration and growout facility. An evaluation of water quality and performance of a similar geotextile bag system was also conducted at the Marine Aquaculture Research Center near Marshallberg, North Carolina, USA, under brackish conditions (15 PPT). Results indicated that performance of each of the systems was similar with TSS, COD, TN, and TP removal greater than 95%, 65%, 50%, and 38%, respectively, for both systems. Analysis of the sludge collected in the freshwater system after 70 days in a dewatering, inactive mode, showed a moisture content (MC) of 86%, or 14% dry matter (DM), indicating the system was effective at passively dewatering the bio-solids. Nutrient removal efficiency may be system specific based on the geotextile bag size and influent flow rate.Geotextile bag systems using flocculant-aids are an efficient means for capturing and dewatering waste solids from RAS effluents. Optimized geotextile bag system designs depend on flow rate, feed rate, and solids dewatering time, and fate of the treated effluent. This evaluation will aid in predicting the expected performance and determining the appropriate size of a geotextile bag system. The type of treatment required downstream from the geotextile bag system used for solids capture in a RAS wastewater treatment system will depend on the intended fate of the treated effluent.     

山东省海水工厂化循环水养殖发展态势与对策研究

本文采用现代情报分析和比较研究方法,以宏观的综合分析为指导,概述了海水工厂化循环水养殖在世界、中国及山东省的发展现状和态势。同时,通过应用专利检索和专利分析方法分析得到了国内外及山东省海水工厂化循环水养殖的研究热点,找出了山东省与国际研究热点的差距,包括养殖水体净化工艺、养殖水体温度调控和养殖池结构设计等单元。最后,基于文献搜集加工与实地调研,结合专利分析结果,指出了山东省海水工厂化循环水养殖业存在的主要问题,并提出了针对发展山东省海水工厂化循环水养殖的对策与建议,为山东省蓝色海洋经济发展提供参考资料。     

Growth performance of disk abalone Haliotis discus hannai in pilot- and commercial-scale recirculating aquaculture systems

The study investigated the growth performance of abalone from juvenile to marketable size in a commercial-scale recirculating aquaculture system. The rearing system consisted of 12 raceways (4.0 × 0.8 × 0.6 m) with a protein skimmer and a submerged biofilter for juveniles and 10 raceways (6.6 × 1.3 × 0.6 m) with a protein skimmer and a trickling biofilter for on-growing. Sea mustard (Undaria pinnatifida) and kelp (Laminaria japonica) were fed to the abalone. The total weight of abalone in the recirculating aquaculture system at the juvenile stage increased from 22.0 kg (average shell length 24.5 mm) to 75.5 kg (average shell length 42.5 mm) after 180 days. Feed conversion ratios increased slightly from 13.7 for the first 90 days to 16.3 thereafter. The shell growth rate of juvenile abalone between 24.5 mm and 34.8 mm was 3.4 mm month⁻¹, while for juveniles between 34.8 mm and 42.5 mm it was 2.6 mm month⁻¹. The total weight of abalone in the recirculating aquaculture system for the on-growing stage increased from 100.0 kg (average shell length 44.0 mm) to 433.3 kg (average shell length 72.7 mm) after 570 days. The feed conversion ratios for the first 173 days, the next 320 days, and the last 570 days were 19.6, 22.1, and 24.8, respectively. The growth rate of the average shell length during the on-growing period was 1.5 mm month⁻¹. Total ammonia nitrogen (TAN) concentrations were stabilized below 0.12 mg l⁻¹ in the juvenile recirculating system and 0.14 mg l⁻¹ in the on-growing recirculating system after conditioning of the biofilters.     

Effects of carbon source addition on microbial community and water quality in recirculating aquaculture systems for Litopenaeus vannamei

Fisheries Science - In order to study the effects of carbon source addition on the bacterial community, water quality and shrimp growth in the recirculating aquaculture system of Litopenaeus...     

工厂化海水养鱼循环系统的工艺流程研究

讨论了一种经济型的封闭式海水养殖水处理技术。包括机械过滤固体废弃物、泡沫分离悬浮物、臭氧消毒、生物膜降解“三态氮”、滴滤除去气态废弃物、贝壳调节pH、氧气罩与溶氧罐混合氧浴增氧等工艺,并就研制的活性生物填料进行了净水实验。结果表明,经过以上系统处理后的水质指标为：COD＜2．8mg／L,SS＜7．2mg／L,非离子氨＜0．02mg／L,细菌含量低于自然海水,养殖牙鲆平均单产为29．92kg／m^2,成活率为95．39％。